Fluid bed incineration catalyst

ABSTRACT

The present invention relates to a process and a catalyst for the fluid bed incineration of a combustible hydrocarbon feedstock. The process comprises contacting the feedstock with a mixture of a fluidized heat transfer media and a combustion promoter catalyst, in the presence of an oxygen-containing gas stream in excess of that required for complete combustion of the carbon monoxide formed, at feedstock combustion conditions. The combustion promoter catalyst consists essentially of particulate with a particle size of greater than 150 microns and includes a promoter metal present in an amount to provide a substantially carbon monoxide-free flue gas.

This application is a division of U.S. patent application Ser. No.07/621,865, filed Dec. 4, 1990, for Fluid Bed Incineration now U.S. Pat.No. 5,101,743.

BACKGROUND OF THE INVENTION

This invention relates to a process and catalyst for the incineration ofa combustible hydrocarbon feedstock. More particularly, this inventionrelates to a process and catalyst for the fluid bed incineration of acombustible feedstock in the presence of a combustion promoter catalystwhere low levels of flue gas carbon monoxide can be attained atfavorably lower combustion temperatures.

The development of efficient methods for reducing the volume of wastes,including hydrocarbon waste, is becoming an important industryobjective. Refineries, petrochemical plants, and public utilities oftenmust dispose of waste hydrocarbon or hydrocarbon fuel that cannot becosteffectively refined or modified into saleable product.Alternatively, land-filling unsalable hydrocarbon is costly, and thecosts escalate with the volume of hydrocarbon, the hazard and toxicityof the hydrocarbon, and its ease of handling. Moreover, landfill spaceis becoming more and more limited. Fluid bed incinerators (FBI) havebeen widely used by industry and public utilities to reduce the volume,toxicity, and facilitate ease of handling of unsalable hydrocarbon bycombusting a substantial portion of the hydrocarbon to carbon dioxideand water.

FBI generally comprise feedstock preparation facilities, a reactorsection, flue gas handling facilities, and solids handling facilities.The reactor section is where the combustion reaction occurs and cancomprise a reactor vessel having a bed of an inert heat transfer media.For purposes of this invention, the term "inert heat transfer media" isdefined as a particulate media substantially incapable of catalyticallyconverting high boiling hydrocarbon into lower boiling gasoline anddistillate. The heat transfer media can be a silica sand or chemicalpellets and can include ash produced in the combustion process. The heattransfer media functions as a heat reservoir for vaporizing waterpresent in the feedstock. The energy supplied to the heat transfer mediafrom the heat of combustion of the FBI feedstock provides most of theheat requirements for feedstock water vaporization but can besupplemented by auxiliary fuel usage.

A problem attendant to FBIs and other processes relying on combustionsteps such as coal gasification and fluidized bed coking is the adverseeffects of incomplete combustion to carbon monoxide. Incompletecombustion of unsalable hydrocarbon is environmentally deleterious andrepresents a wasted source of energy. The further oxidation of carbonmonoxide to carbon dioxide releases approximately 4,350 Btu/lb of carbonmonoxide oxidized.

Industrial and utility operators of FBIs have, in some cases, overcomeincomplete combustion conditions by increasing excess oxygen levels inthe flue gas zone or increasing the flue gas zone temperature, bothfacilitating higher conversion of carbon monoxide to carbon dioxide.Increasing excess oxygen levels is often very costly due the energycosts inherent with adding additional combustion air or oxygen volume tothe flue gas zone, heating this excess volume from ambient conditions tocombustion stack outlet temperatures, and discharging this volume to theatmosphere. Increasing the flue gas zone temperature adversely increasesthe level of metal compound emissions to the atmosphere due to increasedvaporization of these materials in the reactor vessel. Moreover,increasing the flue gas zone temperature inefficiently increases radiantheat losses through the combustion device hardware and, more seriously,causes damage to device hardware.

High flue gas and combustion zone temperatures greatly reduce thehardware life of combustion devices such as FBIs. FBIs can operate attemperatures of from about 500° F. to about 3000° F. and often mustresist abrasion caused by fluidized solids circulating at highvelocities. FBIs, as well as most high temperature combustion devices,are generally equipped with specialized refractory, designed to resisthigh temperature and erosive environments. In spite of modern refractorytechnology, high temperature operation greatly increases the occurrencesof refractory damage, damage to the FBI steel structures, and thefrequency and duration of facility downtime.

While there exists a great need to recognize, identify, and solve theenvironmental and energy related problems associated with incompletecombustion in the process of fluid bed incineration, the art has beendevoid of teachings, and industry has largely acquiesced to the costlysolutions described above.

Carbon monoxide combustion promotion techniques, however, have beentaught for use with other unrelated processes requiring a hydrocarboncombustion step. These techniques have met with varying degrees ofsuccess.

Carbon monoxide combustion promotion has been performed in fluidcatalytic cracking facilities. U.S. Pat. Nos. 4,146,463 (Radford etal.), 4,204,945 (Flanders et al.), 4,252,632 (Mooi), and 4,435,282(Bertolacini et al.) all disclose processes for enhanced conversion ofcarbon monoxide to carbon dioxide in the regenerator section of a fluidcatalytic cracking unit using a combustion-promoting catalyst. Thesecatalysts are either modified cracking catalysts or are added as asupplement to conventional cracking catalysts and are reacted with,attrited, and replenished along with the cracking catalyst before thecombustion promoter catalyst can be deactivated or physically destroyed.As a result, particle attrition through regenerator cyclone systems,particle durability, particulate fluidization, and particulate mixinghave not been as controlling and critical in nature as in the process ofthe present invention. Moreover, promoter catalyst deactivation is lesscritical since the promoted catalyst is continuously replaced. Inpractice, a fluid catalytic cracking combustion promoter would notachieve the process objectives of the fluid bed incineration catalystand process of the present invention (see Example 24).

It is therefore an object of the present invention to provide a processand catalyst for fluid bed incineration that reduces air pollution byachieving reduced flue gas carbon monoxide levels emitted to theatmosphere.

It is another object of the present invention to provide a process andcatalyst for fluid bed incineration that reduces air pollution byachieving reduced flue gas metals levels emitted to the atmosphere.

It is another object of the present invention to provide a process andcatalyst for fluid bed incineration that achieves reduced levels ofhydrocarbon and other products of incomplete combustion (PIC'S) at loweroperating temperatures.

It is yet another object of the present invention to provide a processand catalyst for fluid bed incineration that extends incineratorequipment life, reduces maintenance costs, and reduces the frequency andduration of facility downtime.

It is yet another object of the present invention to provide a processand catalyst for fluid bed incineration with reduced energy costs.

SUMMARY OF THE INVENTION

The above objects can be attained by providing a process for theincineration of a combustible hydrocarbon feedstock comprisingcontacting the feedstock with a fluidized heat transfer media and acombustion promoter, in the presence of an oxygen-containing gas streamin excess of that required for complete combustion of the carbonmonoxide formed, at feedstock combustion conditions, the combustionpromoter catalyst comprising particulates having a particle size ofgreater than 100 microns and having a promoter metal present in anamount to provide a substantially carbon monoxide-free flue gas.

The fluid bed incineration process of the present invention includesaddition of a combustion promoter catalyst that results in substantialreductions in carbon monoxide levels reaching the atmosphere. The carbonmonoxide reduction reduces air pollution and the energy requirementsnecessary to operate the FBI by recovering the heat released fromconverting additional carbon monoxide to carbon dioxide.

The fluid bed incineration process of the present invention results in asubstantially lower operating temperature and lower radiant heat losseswhich result in lower energy costs. In addition, lower operatingtemperatures result in lower routine maintenance costs from repairs ofrefractory and steel damage often incurred during operation. Moreover,new facilities can be constructed with lower thicknesses of lessexpensive refractory and reduced steel thicknesses, saving capitalcosts.

The fluid bed incineration process of the present invention results in asubstantially lower operating temperature which provides forsubstantially lower levels of hazardous metals emitted to theatmosphere. The lower operating temperature reduces metal vaporizationinto the emitted flue gas. Moreover, lower operating temperatures reducethe superficial velocity in the FBI, thereby reducing metal particulateentrainment and the potential for breakthrough into the atmosphere.

The fluid bed incineration process and catalyst of the present inventioninclude addition of a combustion promoter catalyst with high attritionresistance, superior fluidization characteristics, and excellent mixingcharacteristics. The catalyst is also highly resistant to contaminantsinherent in the feedstocks to FBIs and other combustion devices whilemaintaining its ability to oxidize carbon monoxide. The catalyst is notlimited to use in FBIs and can be used in processes such as coalgasification and fluidized bed coking.

A more detailed explanation is provided in the following description andappended claims taken in conjunction with the accompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph describing a typical size distribution for the heattransfer media in an FBI.

FIG. 2 is a graph illustrating the carbon monoxide oxidation curves forseveral combinations of combustion promoter catalyst and heat transfermedia.

FIG. 3 is a graph comparing combustion-promoter catalysts with severalsupport components.

FIG. 4 is a graph comparing equivalent platinum FBI bed loadings using ahigh platinum concentration and a lower platinum concentrationcombustion promoter catalyst.

FIG. 5 is a graph illustrating Geldart fluidization groupclassifications characterized by particle density and particle size.

FIG. 6 is a graph illustrating the minimum fluidization velocity forsilica sand, ash, and catalyst particulate as a function of particlesize.

FIG. 7 is a graph illustrating particle entrainment velocity for silicasand, ash, and catalyst particulate as a function of particle size.

FIG. 8 is a graph illustrating particle mixing index for mixtures ofcatalyst and ash, catalyst and silica sand, and silica sand and ash as afunction of superficial velocity.

FIG. 9 is a graph illustrating the effects of sludge deposits andtypical FBI process conditions on the combustion promoter catalystcarbon monoxide oxidation curves.

DETAILED DESCRIPTION OF THE INVENTION

The feedstock for use in the incineration process of the presentinvention can comprise most materials that are combustible in thepresence of oxygen at temperatures within the operating range of theincineration device. These materials are generally, but not limited to,hydrocarbons.

FBI feedstocks can comprise hydrocarbon streams produced in a refineryor petrochemical plant such as waste streams and by-product streams.Waste streams can comprise materials recovered from the reclamationareas of a petroleum refinery or petrochemical plant including, but notlimited to, air flotation tank hydrocarbon skimmings, oil/waterseparator sludge, and biopond sludge. FBI feedstocks can also compriseby-product streams from a petroleum facility or petrochemical plant thatmay prove too costly or difficult to reprocess into saleable productssuch as off-specification or used lubricating oils having high metaladditives which are often detrimental to catalytic processes, spentcaustic, spent solvents, chlorine-containing feeds, and storage tankcleaning deposits.

FBI feedstocks can also comprise feedstocks from utilities includingenergy producing utilities and sanitation utilities. The process of thepresent invention can apply, in the energy sector, to the combustion ofcoal and residual coke in energy producing facilities using the fluidbed combustion of fuel sources. The process of the present invention canalso apply to utilities that incinerate municipal wastes such asmunicipal solid waste, sewage sludges, and hospital waste.

FBI feedstocks can also range widely in water content extending fromtrace amounts of water to as much as 90 percent by weight water. Highwater contents are often inherent to oil collection devices found inrefinery, petrochemical plant, or utility devices such as, but notlimited to, separators, skimmers, and filter presses.

Similarly, FBI feedstocks can also contain a substantial amount ofsolids, some of which can be recovered through refinery or petrochemicalplant reclamation facilities. An FBI feedstock can comprise as much as50 percent by weight solids but more typically will comprise from zeropercent to 25 percent solids by weight.

Since the process of the present invention can have application inprocesses other than FBIs and energy producing utilities havingcombustion devices such as a petroleum refinery fluidized bed coker anda petroleum refinery fluid catalytic cracking unit, the feedstock cancomprise coked catalyst, residual coke, or other suitable combustiblematerials.

In accordance with the present invention, the combustion promotercatalyst comprises a combustion-promoting metal dispersed on a catalystsupport. The support for the oxidation catalyst can be lesscatalytically active or even inert to the oxidation reaction. Desirably,the support is porous and has a surface area as determined by testmethod ASTM D-3663-84, including the area of the pores on the surface,of at least from about 2 m² /gm to about 250 m² /gm, preferably fromabout 50 m² /gm to about 200 m² /gm, and more preferably from about 80m² /gm to about 150 m² /gm for best results. Suitable supports for usein the present invention include mullite, spinel, sand, silica, alumina,silica alumina, titania, zirconia, alpha alumina, gamma alumina, deltaalumina, and eta alumina. Supports comprising alpha alumina, gammaalumina, silica, or silica alumina are preferred. Supports comprisingalpha alumina or gamma alumina are more preferred.

The support component of the combustion promoter catalyst can be pure ora composite of materials. Composite supports are advantageous wherethere is a desire to add particular chemical or physical characteristicsto the combustion promoter catalyst. For example, the promoter catalystcan comprise a substrate and a substrate coating in order to attain theparticular benefits of both substrate materials having high attritionresistance and substrate coating materials having high surface area. Thesubstrate and substrate coating can be combined through conventionalimpregnation techniques, controlled calcination, mechanical deposition,and coating. Suitable materials for use as a composite substrate for thecombustion promoter catalyst are mullite, spinel, alpha alumina, andsand. Alpha alumina is the preferred composite substrate. Suitablematerials for use as a composite substrate coating are silica, alumina,titania, silica alumina, zirconia, gamma alumina, delta alumina, and etaalumina. Composite substrate coatings comprising silica, silica alumina,and gamma alumina are preferred. Composite substrates comprising gammaalumina are more preferred.

The combustion-promoting metal of the process of the present inventioncan be the types used or generally known in the art to promote theoxidation of carbon monoxide to carbon dioxide in the presence ofmolecular oxygen. The metal can be in a combined form, such as an oxide,rather than being in the elemental state. The combustion-promoting metalcan comprise two or more catalytically-active metals either physicallyor chemically combined. Suitable combustion-promoting metals for use inthe process of the present invention are the transition group elementsof the Periodic Table (IUPAC), preferably the Group VIII metals, morepreferably the platinum metals, and more preferably yet, platinum.Platinum is preferred by reason of its ability to sustain high activityfor oxidation of carbon monoxide.

The percentage of combustion-promoting metal to add to the combustionpromoter catalyst used in the present invention is a function ofcatalyst cost and process effectiveness. The preferred concentration ofpromoter metal is that which achieves process objectives at minimumcatalyst cost. Generally, the combustion-promoting metal is the mostcostly component of the combustion-promoting catalyst. Higher metalconcentrations and lower volume usages reduces the combustion promotersupport and catalyst manufacturing costs but can require higher metalamounts due to the potential for reduced mixing within the FBI heattransfer media. Lower metal concentrations and higher volume usagesreduce the metal requirements due to better mixing within the heattransfer media, but require additional promoter support and catalystproduction costs. Suitable metal concentrations on the combustionpromoter catalyst of the present invention can range by weight fromabout 10 ppm to about 5000 ppm, preferably from about 50 ppm to about3000 ppm, and more preferably from about 100 to about 2500 ppm for bestresults. The combustion promoter catalyst metal concentration is basedon a platinum level within the heat transfer media of an FBI by weightof from about 0.1 ppm to about 10 ppm, preferably from about 0.5 ppm toabout 5 ppm, and more preferably from about 1 to about 3 ppm for bestresults.

A platinum group component can be incorporated in the support in anysuitable manner, such as by coprecipitation or cogellation with thesupport, ion-exchange, or by impregnation. Preferably, the platinumgroup component is substantially uniformly dispersed on the support. Onepreferred method for adding the platinum group component to the supportinvolves the utilization of a water soluble compound of the platinumgroup component to impregnate the support prior to calcination. Forexample, platinum may be added to the support by commingling theuncalcined support with an aqueous solution of chloroplatinic acid.Other water soluble compounds of platinum may be employed asimpregnation solutions, including for example, ammonium chloroplatinate,platinum chloride, and tetraammineplatinum.

The combustion promoter catalyst used in the present invention shouldhave the proper physical characteristics for use in fluid bedincineration. The most important physical characteristics in thepractice of the present process are particle size and density, Geldartfluidization group, minimum fluidization and entrainment superficialvelocities, and mixing characteristics.

The fluidization characteristics of particles, classified by size anddensity, are described by Geldart, D., "Gas Fluidization Technology",Wiley-Interscience, 1986, the teachings of which are herein incorporatedby reference. The Geldart Fluidization Diagram is illustrated in FIG. 5.Group A materials, like fluid catalytic cracking catalyst, are easilycirculated; fluidization properties are influenced by interparticleforces; and beds comprising Group A materials collapse slowly when thefluidization gas is shut off. Group B materials, such as silica sand, donot fluidize as easily as Group A materials, have negligibleinterparticle forces, achieve small bed expansion upon fluidization, andthe expanded bed collapses rapidly upon loss of fluidization gas. GroupC materials, such as flour and some plastics, are cohesive andfluidization is extremely difficult. Group D materials are subject topoor backmixing, and the particles tend to segregate by size.

The heat transfer media of an FBI can comprise silica sand or chemicalpellets and can generally contain ash material produced during theincineration process. The ash particles can have different size anddensity physical properties than the heat transfer media itself (seeFIG. 5) and can, under some operations, comprise from zero percent byweight to as much as 90 percent by weight of an FBI bed. Although ashand silica sand can have different physical properties, they are bothGroup B materials and behave similarly in fluidization. As a result,Group B and Group A particles, and more preferably Group B particles arepreferred for use as the heat transfer media and as the combustionpromoter catalyst of the present invention.

The combustion promoter catalyst should be selected with properfluidization superficial velocity characteristics. Superficial velocityis the volumetric flowrate of a stream per cross-sectional area of thevessel. In an FBI, superficial velocity is a dependent variable subjectto the dimensions of the FBI reactor, the amount and characteristics ofthe feedstock, and the amount of oxygen-containing gas used to combustthe feedstock at the given feedstock feedrate. If the superficialvelocity in an FBI is higher than the minimum superficial fluidizationvelocity of the particulate, the particles will fluidize. Smallerparticles fluidize at lower superficial fluidization velocities thanlarger particles, as is illustrated in FIG. 5 which is derived fromGeldart (see Geldart, pages 21-24).

The combustion promoter catalyst should also be selected to minimizeparticle carryover and entrainment into the flue gas. Particulatecarryover requires larger particulate recovery systems (e.g., cyclones),reduces particulate recovery system life, results in higher particulateattrition, and often results in greater particulate losses. Particulateentrainment and carry-over generally occurs when the superficialvelocity in an FBI reactor exceeds the terminal velocity of a particle.Some carryover is additionally caused by collisions and momentumexchange with the particulate fines being carried over, but thiscarryover contribution has generally been determined to be minor in aproperly designed FBI.

Particulate entrainment and carryover is minimized by selecting acombustion promoter catalyst that maximizes the superficial velocity atwhich particulate entrainment and carryover begins to occur. FIG. 7provides curves relating particle terminal velocity to particle massaverage diameter for typical catalyst, ash, and silica sand particulates(see Example 17). The curves are slightly different for each particlebecause of differing particle densities. Particle entrainment andcarryover is a function of particle size wherein larger particle sizesrequire higher superficial velocities to entrain and carry-over theparticle. As a result, larger particles are preferred over smallerparticles to reduce particulate entrainment and carryover. Therefore,the preferred combustion promoter catalyst will have physical propertiessuitable for ease of fluidization while providing resistance toparticulate entrainment and carryover.

For the above reasons, the combustion promoter catalyst particles of thepresent process and catalyst should substantially exceed 100 microns inparticle diameter, preferably 150 microns in particle diameter, and morepreferably 200 microns in particle diameter for best results. Thecombustion promoter catalyst should generally contain at least 80% byweight particles having these properties, preferably at least 90% byweight, and more preferably at least 95% by weight for best results.

The combustion promoter catalyst should be selected to provide suitablemixing characteristics with the components of the heat transfer mediawhich can include sand and ash components. Although a bed of heattransfer media and combustion-promoting catalyst may be well fluidizedin the sense that all particles are fully supported by the gas, the bedmay still be segregated, in that the local composition of a particularzone does not correspond to the overall average composition in thereactor vessel. Segregation is more likely to occur when the mediacontains particles of different densities than when the size range isvery broad. Nienow, Rowe, and coworkers have investigated segregation bydensity difference and have proposed a useful correlation for predictingthe critical superficial velocity at which mixing takes over fromsegregation (see Geldart, pages 110-114). The correlation depends onparticle density, minimum fluidization velocity, and particle size. Themixing index can be calculated from the critical mixing velocity. Themixing index is an arbitrary scale which varies from 0 (completehorizontal segregation in the bed) to 1 (perfect mixing).

FIG. 8 illustrates mixing index curves for typical catalyst, ash, andsilica sand particulate as a function of superficial velocity (seeExample 18). The catalyst and ash particulates are closely related indensity while the catalyst and silica sand particulates are closelyrelated in particulate size. FIG. 8 illustrates that particulatemixtures that are proximate in particulate density provide the bestmixing characteristics. For the process of the present invention, it ispreferable that the combustion promoter catalyst and heat transfer mediaparticulate (including the ash and the media), have a mixing index of atleast 0.3, preferably of at least 0.4, and more preferably of at least0.5 for best results.

The combustion promoter catalyst and the process mechanics of the FBIshould be selected to minimize catalyst and heat transfer mediaattrition. A catalyst or heat transfer media that undergoes attritioneasily increases operational costs by requiring more frequent solidsadditions and can result in additional particulate fines entering theatmosphere or being recovered for disposal.

Particulate can undergo mechanical or chemical attrition. Mostmechanical attrition in an FBI occurs at the combustion gas distributorwhere a high velocity oxygen-containing gas generally contacts the FBIheat transfer media. It is preferred that combustion gas distributionsystems be selected to minimize impinging contact with particulate.Mechanical attrition is also reduced by leaving at least a portion ofthe ash components in the heat transfer media bed. In comparing ash anda typical heat transfer media component such as silica sand, the ash issofter, can be about four times smaller in mass average diameter, andcan be about half as dense, indicating that the ash can provide acushioning mechanism for a combustion-promoting catalyst. Therefore,some ash within the FBI heat transfer media is preferred over a mediaconsisting largely of a component such as silica sand.

Particulate such as FBI heat transfer media or an FBI combustion,promoting catalyst can also be chemically attrited. When particulate inan on-stream FBI is suddenly exposed to large volumes of awater-containing feedstock or when a catalyst in a previously shutdownFBI that has accumulated water is heated up too quickly, water trappedinside the catalyst can quickly vaporize and shatter the catalyst.Support components of the combustion promoter catalyst that are durableand chemical attrition resistant are preferred in the process of thepresent invention. Similarly, procedural safeguards against theattrition hazards of water during FBI startups and routine operationshould be implemented for best results.

The combustion promoter catalyst generally will not deactivate fromexposure to most FBI feedstocks. FBI feedstocks having sludge as aningredient may also contain a variety of metal components (see Table 1)that can reduce the effectiveness of some catalytic processes. However,exposure of the catalyst used in the present process to feedstockshaving metal-containing sludges generally does not deactivate thecatalyst. In many cases, carbon monoxide oxidation performance improveswith sludge addition since the sludge can possess additionalcombustion-promoting metals. Therefore, catalyst deactivation fromsludges and metals containing feedstocks generally does not adverselyeffect the process of the present invention.

Typical FBI facilities have process sections including feedstockpreparation facilities, a reaction section, flue gas handlingfacilities, and solids handling facilities. The feed preparationfacilities can extend upstream in the processing scheme to includeskimming devices on air flotation equipment, separator devices, andother reclamation operations where the waste feedstock is recovered.Waste streams are generally gathered from these devices in anaccumulator for further feedstock preparation. The feedstock preparationfacilities can have a preliminary water separation device which can be avessel having weirs designed to separate and remove water from FBIfeedstock by gravity differences. A similar separation can be achievedwith a storage tank having water drawing facilities. Still anothermechanism for reducing the level of water in sludge is through beltfilter presses which mechanically assist in the water separationprocess. The water separation process is often assisted by addition ofdewatering additives that can facilitate water/feedstock separation.Excessive water quantities should be removed from the FBI feedstockbefore proceeding to the FBI for best results.

The reaction section of an FBI generally includes a reaction vesselwherein the combustion reaction takes place. The reaction vesselincludes a bed of inert heat transfer media which can comprise silicasand, chemical pellets, or other suitable materials for providing thefunction of absorbing heat from the combustion reaction and transferringthe heat to the feedstock. The heat transfer media generally willaccumulate ash components produced during the combustion reaction. Thecombustion promoter catalyst of the process of the present invention isadded to the reactor vessel and disperses with the heat transfer mediaand ash component. It is important that the combustion-promotingcatalyst have the proper physical characteristics for use in fluid bedincineration. The most important physical characteristics are those ofparticle size and density, Geldart fluidization group, fluidizationsuperficial velocity properties, and mixing capability.

Combustion gas injection coils are generally designed below the heattransfer media bed for providing an oxygen-containing combustion stream(generally air) for the incineration reaction and for fluidizing themedia, ash, and combustion promoter catalyst. Fluidization increases theparticulate heat transfer and combustion promoter catalyst surface areaavailable for contact with the feedstock. The air injection coils can bein a ring form or any suitable design to provide an even distribution ofair flow across the bed.

The reactor vessel is also generally equipped with feedstock injectionnozzles which are designed to introduce feedstock to the FBI. Thenozzles can be equipped with an atomizing stream to reduce the particlesize of the feedstock upon entry into the incinerator. Atomizationpromotes quicker and more complete combustion of the feedstock. Asuitable atomization stream is steam. The reactor vessel may also beequipped with fuel injection nozzles. The fuel injection nozzles areprovided for conditions where the heat released from combustion of thefeedstock is insufficient to vaporize the water component in the feedand the temperature necessary to maintain proper combustion conversioncannot be maintained. The fuel flow to the injection nozzles can oftenbe controlled, through use of suitable instrumentation, by thetemperature of the FBI flue gas. The fuel nozzles can also be atomizedwith an atomization stream such as steam. The fuel injected into reactorvessel can also be injected into the feedstock prior to entry into thereactor vessel. In these designs, a fuel injection nozzle projecteddirectly into the reactor vessel may not be required for routineoperations.

The reactor vessel is also generally equipped with a particulate removalsystem which can include cyclones to remove particulates from the fluegas prior to exiting the reactor vessel. FBI cyclone systems are oftendesigned to substantially recover particulates of greater than a minimumparticle size. A suitable minimum particle size for cyclone design canrange from about 1 micron to about 50 microns but will generally rangefrom about 2 microns to about 20 microns. These particles exiting thecyclones drop downwardly through cyclone diplegs and can be returned tothe heat transfer media bed or can be dropped to a particular storagedevice, often for disposal. The particulate removal system operates toreduce the particle size of materials exiting the reactor vessel withthe flue gas to very small particulate diameters.

The flue gas handling system generally operates with the objective ofrecovering waste heat from the flue gas and utilizing the waste heat forthe production of steam or electricity or for transfer back to theprocess. Moreover, the flue gas handling system operates to furtherremove small particulate from the flue gas before discharging the gas tothe atmosphere. These handling facilities often begin with a waste heatrecovery unit. The waste heat recovery unit can be an air preheaterwhich is often designed to transfer heat to the combustion air oroxygen-containing gas stream used in the combustion process from theflue gas exiting the reactor vessel. The waste heat recovery unit canalso be a facility where the heat supplied by the flue gas is used togenerate steam or electricity.

A second objective of the flue gas handling system is to further removesmall particulates from the FBI flue gas that escape the cycloneparticulate removal system. This can be done through use of a bag house.However, bag houses do not operate as effectively in FBI operationswhere the feedstock has a high water content. High water content fluegases can result in bag house pluggage, lower operating factors, andhigh maintenance costs. Another means of recovering small particulatefrom flue gas is through a scrubber mechanism. In scrubber systems, theflue gas can be induced through a Venturi mechanism by steam ejectors,and the steam and flue gas condensed in a vented barometric condenser.Condensation cooling can be provided by conventional heat exchangermeans or by direct contact with a suitable cooling stream such as water.The non-condensibles are vented to the atmosphere while the smallparticulates generally remain with the condensate (and barometric waterif applicable) phase. The small particulates can be recovered from thecondensate phase through use of settling vessels with or withoutaddition of conventional anti-floculent chemicals, and the water can beremoved for further purification.

The solids handling facilities function to permit solids addition andremoval to and from various locations on the process. Additions aregenerally performed to restore attrited solids levels and supplement theheat transfer media with the combustion promoter catalyst of the processof the present invention. Solids additions are generally performed bygravity flow from supply bins located above the elevation of the processinjection point. Particulate can be staged to the bins by elevators orby other suitable means. The process can have solids addition points atthe reactor bed, at the inlet to the supply bins, and at the inlet tothe solids elevators. Solids removal is performed to selectively removesolids from the process where the operator may want to lower the overallsolids level or lower the concentration of a particularly sized solid.Solids removal is also performed by gravity flow. The process can havesolids removal points at the FBI bed and the reactor vessel cyclonediplegs. The cyclone dipleg removal point will permit selective removalof smaller sized particulate.

The fluid bed incineration process of the present invention generallybegins with the accumulation of an FBI feedstock and preliminaryfeedstock preparation steps such as gross dewatering. The feedstock isinjected into a reaction vessel containing a fluidized heat transfermedia commingled with a combustion-promoting catalyst with particularphysical characteristics, in the presence of an oxygen-containing streamhaving oxygen in excess of that necessary for complete conversion ofcarbon monoxide to carbon dioxide. The catalyst entrained in the fluegas produced in the combustion reaction is separated from the flue gasin a particulate recovery system and returned to the heat transfermedia. The flue gas leaving the reactor is cooled in a waste heatrecovery facility, smaller catalyst fines are further removed from theflue gas, and the flue gas is discharged to the atmosphere.

One important process variable in an FBI operation is combustiontemperature. Combustion temperature is maintained at sufficiently hightemperatures to ensure environmentally safe carbon monoxide conversionlevels. These temperatures are often in excess of 1200° F. The FBI ofthe present invention should be operated to emit a substantially carbonmonoxide-free flue gas to the atmosphere. FBI carbon monoxide emissionslevels in the vented flue gas should be maintained below 500 ppm byweight, preferably below 250 ppm by weight, and more preferably below100 ppm by weight. The process of the present invention can be operatedto attain levels of 10 ppm by weight or lower of carbon monoxide in thevented flue gas.

While high combustion temperatures promote carbon monoxide conversion,they adversely increase the level of metals emitted to the atmosphere.Elevated operating temperatures result in higher metals emissions sincethey promote higher levels of metal vaporization into the flue gas.Moreover, higher temperatures result in higher reactor superficialvelocities, additional entrained particulate, and the potential forparticulate breaking through the cyclone particulate removal systemswhich can result in higher metal levels entering the atmosphere. Theprocess of the present invention permits attaining of high carbonmonoxide conversion levels while minimizing operating temperature so asto also reduce metals emissions to the atmosphere.

Lower maintenance costs and higher operating factors are an attendantbenefit to operating an FBI at lower temperatures. Higher temperatureoperations create higher reactor vessel superficial velocities, creatingadditional solids internal abrasion. Higher temperature operationstypically require greater thicknesses of higher cost refractory inaddition the costs of increasing the refractory wear resistance. FBIsthat operate at higher temperatures generally incur more frequent FBIshutdowns and longer and more costly repairs.

Solids physical characteristics is another process parameter whichshould be controlled to achieve the objectives of the process of thepresent invention. The combustion promoter catalyst should conform tothe requirements of particle size and density, Geldart fluidizationproperties, fluidization superficial velocity properties, and mixingcharacteristics described above. For example, addition of acombustion-promoting catalyst having a substantial portion of particlesbelow 100 microns added to a heat transfer media with generallydifferent physical properties would not operate as effectively as theprocess of the present invention.

The present invention is described in further detail in connection withthe following examples, it being understood that the same are forpurposes of illustration only and not limitation.

EXAMPLE 1

A combustion promoter catalyst was prepared by dispersing gamma alumina(Versal GH alumina-manufactured by La Roche Chemicals in distilled waterand nitric acid and forming a solution with a pH of 3. The dispersionwas used to impregnate low surface area alpha alumina (Fluidizable LowSurface Area Alumina--Product 6595--manufactured by Norton), and theresulting coated substrate was dried over night at 250° F. The coatedsubstrate was then sieved to remove particles less than 325 mesh (44microns). The coated substrate had a surface area of 28 m² /g. Thecoated substrate was impregnated with chloroplatinic acid, dried, andcalcined at 1000° F. providing a combustion promoter catalyst with 2000ppm platinum.

EXAMPLE 2

Spent fluid bed incinerator media was obtained from a fluid bedincinerator located at the Amoco Oil Whiting Refinery in Whiting, In.The material was sieved into several fractions, and each fraction wasanalyzed for density using mercury porosimetry. The results areillustrated in FIG. 1.

The size distribution is bimodal and reflects a media containing silicasand and ash. The smaller mode density, which is attributed to the ashfraction, is nearly constant at 1.5 g/cm, and the larger mode, which isattributed to silica sand, has a density of about 2.4 g/cm. The massaverage diameters of the sand and ash fractions were found to be 940microns and 230 microns, respectively. The Geldart fluidizationcharacteristics placed the catalyst as a Group B material (see FIG. 5).The silica sand made up about 30 percent by weight of the media.

EXAMPLE 3

Fresh silica sand having a mode density of about 2.3 g/cm, a massaverage diameter of 790 microns, and a size range of from 710 microns to850 microns was tested for its ability to oxidize carbon monoxide. Thetests were done with 25 gm of catalyst in a 23 mm ID quartz tube with atotal flow of 150 ml/min of gas. The composition of the gas was 505 ppmcarbon monoxide, 15 percent by volume oxygen, and the balance nitrogen.The weight percent conversion of carbon monoxide to carbon dioxide wasmeasured from room temperature to 1500° F. The results are illustratedin FIG. 2.

The FBI process using fresh silica sand does not enhance the oxidationof carbon monoxide to carbon dioxide.

EXAMPLE 4

The spent fluid bed incinerator media of Example 2 was tested for itsability to oxidize carbon monoxide using the testing technique ofExample 3. The results are illustrated in FIG. 2.

The FBI process using the spent fluid bed incinerator media of Example 2provides better oxidation characteristics than the process using freshsilica media since the spent media contains metal deposits from contactwith FBI feedstocks that can assist in carbon monoxide oxidation tocarbon dioxide.

EXAMPLE 5

The catalyst of Example 1 was added to the fresh silica sand describedin Example 3 such that the bed contained 2 ppm by weight of platinum insilica sand. The bed was subjected to the testing technique of Example3. The results are illustrated in FIG. 2.

The FBI process using the combustion promoted silica sand of Example 5provides 95 percent by weight carbon monoxide conversion at a 1000° F.lower temperature than the process using the fresh silica sand alone ofExample 3.

EXAMPLE 6

The catalyst of Example 1 was added to the spent fluid bed incineratormedia of Example 2 such that the bed contained 2 ppm by weight ofplatinum in silica sand. The mixture of spent media and catalyst wassteamed at 1400° F. for 5 hrs to simulate FBI reactor conditions. Thebed was subjected to the testing technique of Example 3. The results areillustrated in FIG. 2.

The FBI process using the combustion promoted spent fluid bedincinerator media of Example 6 provides 95 percent by weight carbonmonoxide conversion at a 700° F. lower temperature than the processusing the spent fluid bed incinerator media alone of Example 4.

EXAMPLE 7

The mixture of spent media and catalyst of Example 6 was steamed at1400° F. for 66 hrs to simulate more severe FBI reactor conditions. Thebed was subjected to the testing technique of Example 3. The results areillustrated in FIG. 2.

The FBI process using the combustion promoted spent fluid bedincinerator media of Example 7 provides 95 percent by weight carbonmonoxide conversion at a 400° F. lower temperature than the processusing the spent fluid bed incinerator media alone of Example 4. The FBIprocess using the sample of catalyst and media of Example 7, steamed for66 hrs instead of the 5-hour steaming of the process of Example 6provided better carbon monoxide conversion performance below a level of72 percent by weight conversion and worse performance as conversionincreased beyond 72 percent by weight.

EXAMPLE 8

A combustion promoter catalyst was prepared by impregnating gammaalumina (Intercat) with chloroplatinic acid to form a combustionpromoter catalyst having 100 ppm of platinum. The mass average diameterof the combustion promoter catalyst ranged from 460 microns to 1400microns. The catalyst was added to a bed of the fresh silica sanddescribed in Example 3 above to form a bed with a platinum concentrationof 2 ppm by weight.

The catalyst was subjected to the testing technique of Example 3. Theresults are illustrated in FIG. 3.

EXAMPLE 9

A combustion promoter catalyst was prepared by impregnating alphaalumina (Norton) with chloroplatinic acid to form a combustion promotercatalyst having 100 ppm of platinum. The mass average diameter of thecombustion promoter catalyst ranged from 500 microns to 1000 microns.The catalyst was added to a bed of the fresh silica sand described inExample 3 above to form a bed with a platinum concentration of 2 ppm byweight.

The catalyst was subjected to the testing technique of Example 3. Theresults are illustrated in FIG. 3.

The FBI process using the combustion promoter catalyst of Example 9having alpha alumina, provided inferior performance to the process usingthe combustion promoter catalyst of Example 8 having gamma alumina,across all ranges of carbon monoxide conversion.

EXAMPLE 10

A combustion promoter catalyst was prepared by coating the alpha aluminaof Example 9 with the gamma alumina of Example 1, using the proceduredescribed in Example 1, and impregnating the coated substrate withchloroplatinic acid to form a catalyst having 100 ppm of platinum. Themass average diameter of the combustion promoter catalyst ranged from500 microns to 1000 microns. The catalyst was added to a bed of thefresh silica sand described in Example 3 above to form a bed with aplatinum concentration of 2 ppm by weight.

The catalyst was subjected to the testing technique of Example 3. Theresults are illustrated in FIGS. 3 and 4.

The FBI process using the combustion promoter catalyst of Example 10,having alpha alumina impregnated with gamma alumina, provided inferiorperformance to the process using the combustion promoter catalyst ofExample 8 having gamma alumina across all ranges of carbon monoxideconversion. The process using the catalyst of Example 10 providedcomparable performance to the process using the catalyst of Example 9having alpha alumina below 72 percent by weight carbon monoxideconversion and superior performance above 72 percent by weight carbonmonoxide conversion.

EXAMPLE 11

A combustion promoter catalyst similar to the catalyst of Example 10 wasprepared but for impregnation of the coated substrate withchloroplatinic acid to form a catalyst having 2000 ppm platinum. Thecatalyst was similarly added to a bed of the fresh silica sand describedin Example 3 above to form a bed with a platinum concentration of 2 ppmby weight.

The catalyst was subjected to the testing technique of Example 3. Theresults are illustrated in FIG. 4.

FIG. 4 illustrates that lower platinum levels on the combustion promotercatalyst at similar platinum concentrations in the bed (i.e., higherconcentrations of catalyst in the fresh silica sand) provides bettercarbon monoxide conversion. This is largely due to better platinumdispersion in the bed.

EXAMPLE 12

A catalyst was prepared for testing catalyst attrition resistance bysieving a sample of gamma alumina (Intercat) particles into fractions.The catalyst consisted of gamma alumina particles with a mass averagesize of 720 microns, a size range of from 710 microns to 850 microns,and a particle density of 1.2 g/cm. The Geldart fluidizationcharacteristics placed the catalyst as a group B material (see FIG. 5).The catalyst was spherical with a sphericity factor of unity.

EXAMPLE 13

A mechanical attrition test was conducted in a 4-inch ID plexiglas modelfluid bed incinerator. The catalyst of Example 12 was added to the spentfluid bed incinerator media of Example 2 such that the mixture ofcatalyst and media was 1 percent by weight catalyst. The mixture wasfluidized by air at ambient conditions for 7 days. The superficialvelocity of the air in the model was maintained at 0.7 m/sec to simulatetypical fluid bed incinerator conditions. The gas velocity across theair distributor openings was maintained at 3.2 m/sec to simulate typicalfluid bed incinerator conditions. The gamma alumina catalyst proved tobe highly attrition resistant producing less than 1 percent by weightfines below 425 microns.

EXAMPLE 14

A mechanical attrition test was conducted in a 1-inch ID glass tube atsimilar conditions to those in Example 13. The catalyst of Example 12was added to a bed of the silica sand described in Example 3 such thatthe mixture of catalyst and silica sand was 4 percent by weightcatalyst. After 24 hours, the catalyst produced about 10 percent finesindicating that the ash in the fluid bed incinerator media favorablylowers the catalyst attrition rate. This is likely a result of thecushioning effect of the ash.

EXAMPLE 15

A chemical attrition test was conducted on the catalyst of Example 12 tosimulate contact of the combustion promoter catalyst in an FBI withsteam. The catalyst was impregnated with water and dropped onto a hotplate in a furnace at 1500° F. The catalyst remained intact and did notshatter.

EXAMPLE 16

The minimum fluidization superficial velocity was determined in the4-inch ID plexiglas fluid bed incinerator model. The catalyst of Example12 was added to the spent fluid bed incinerator media of Example 2 suchthat the mixture of catalyst and media was 1 percent by weight catalyst.In the plexiglas column, bubbles began to form at a 0.018 m/secsuperficial velocity and were discernibly produced at a superficialvelocity of 0.025 m/sec. The bubble formation reflected fluidization ofthe ash component of the mixture since the ash particles have thesmallest particle size and are first to fluidize. FIG. 6 illustrates thepredicted minimum superficial fluidization velocities of the ash,catalyst, and silica sand components of the mixture as predicted byGeldart (see Geldart, pages 21-24) and the actual ash minimumsuperficial fluidization velocity data point.

EXAMPLE 17

The minimum particle entrainment velocity was predicted using Geldart(see Geldart, pages 123-153) for the catalyst of Example 12, ash (1.5g/cm, 230 micron mass average diameter), and the silica sand of Example3. The findings are illustrated in FIG. 7.

FIG. 7 provides curves for the catalyst, ash, and silica sand, eachdiffering slightly because of their particle density differences. FIG. 7also illustrates that the terminal velocity for ash is lower than thatof the catalyst and the sand due to its particle size and would entrainfirst in a mixture of the three particulate components upon FBIsuperficial velocity exceeding the terminal velocity of the ash. FIG. 7also illustrates the benefits of selecting a combustion promotercatalyst with larger particle size than the ash.

EXAMPLE 18

The mixing index for binary mixtures of the catalyst of Example 12 andash (1.5 g/cm, 230 micron mass average diameter), ash and the silicasand of Example 3, and the catalyst and the silica sand were predictedfor varying levels of superficial velocity. The mixing index correlationis by Neinow, Rowe, and coworkers and reported in Geldart (see Geldart,pages 110-114). The findings are illustrated in FIG. 8.

FIG. 8 illustrates that the catalyst/ash mixture provides the bestmixing, followed by the catalyst/silica sand mixture, and lastly by thesilica sand/ash mixture. FIG. 8 further illustrates that the degree ofmixing is largely a function of the relative similarities in particledensity.

EXAMPLE 19

Catalyst and FBI media mixing was tested in the 4-inch ID plexiglasfluid bed incinerator model. The catalyst of Example 12, which was whitein color, was placed on top of the fluid bed incinerator media ofExample 2, which was rust in color, without any air flow. The air flowwas added and increased to typical fluid bed incinerator superficial gasvelocities of about 0.65 m/sec. The catalyst was quickly dispersed inthe bed. There were short periods of time where pockets of the bed werenot circulated but overall, the catalyst was well-dispersed in themedia.

EXAMPLE 20

A base case for catalyst deactivation tests was developed by adding acatalysst consisting of gamma alumina (intercat), absent a promotermetal to the pilot plant of Example 3. The catalyst was subjected to thegas of Example 3, and the percent by weight carbon monoxide conversionwas measured from room temperature to 1300° F. The results areillustrated in FIG. 9.

EXAMPLE 21

A second base case for catalyst deactivation tests was developed byadding a catalyst consisting of gamma alumina (Condea/Intercat)impregnated with 200 ppm of platinum to the pilot plant of Example 3.The catalyst was subjected to the gas of Example 3, and the percent byweight carbon monoxide conversion was measured from room temperature to1300° F. The results are illustrated in FIG. 9.

FIG. 9 illustrates that the fresh platinum impregnated gamma aluminacatalyst of Example 21 performs better than the gamma alumina withoutplatinum impregnation.

EXAMPLE 22

Catalyst deactivation from contact with FBI sludges was measured for thecombustion promoter catalyst of Example 21. A mixture of 20 gm ofcatalyst and 20 gm of a typical FBI sludge feedstock having thecomponents described in Table 1 was prepared and dried at 250° F. for aperiod of 2 hrs to remove volatile components. The catalyst and sludgemixture was further heat dried in a combustion tube at 1250° F. for 1 hrin the presence of air flowing at 100 cc/min. The catalyst and sludgedeposits were added to the pilot plant described in Example 3. The gasof Example 3 was added to the pilot plant containing the catalyst andsludge deposits and the percent by weight carbon monoxide conversion wasmeasured from room temperature to 1300° F. The results are illustratedin FIG. 9.

FIG. 9 illustrates that the catalyst does not deactivate in the presenceof typical FBI sludge. In fact, carbon monoxide conversion is improvedas compared to the fresh catalyst of Example 21, due to the presence ofadditional promoting metals present in the sludge deposits.

                  TABLE 1                                                         ______________________________________                                        FBI Sludge Feedstock                                                          Component     ppm by weight                                                   ______________________________________                                        Zn            1250                                                            Mn             23                                                             Pb            18800                                                           Cr            410                                                             Fe            2040                                                            Ni             18                                                             V              22                                                             Cu            228                                                             Co             4                                                              Na            4900                                                            K             359                                                             Ca            730                                                             Mo            157                                                             Mg            1480                                                            Al            450000                                                          Ti             45                                                             P             1740                                                            Sr             62                                                             ______________________________________                                    

EXAMPLE 23

Catalyst deactivation from contact with FBI sludges was measured for thecombustion promoter catalyst and sludge deposits of Example 22 adding acatalyst steaming step to simulate the adverse conditions experienced inan FBI. After the heat drying step of Example 22, the catalyst andsludge deposits were steamed at 1250° F. for 1 hr with steam. The gas ofExample 3 was added to the pilot plant containing the steamed catalystand the sludge deposits, and the percent by weight carbon monoxideconversion was measured from room temperature to 1300° F. The resultsare illustrated in FIG. 9.

FIG. 9 illustrates that the catalyst is not adversely affected ordeactivated by the presence of steam in an FBI. In fact, carbon monoxideconversion is improved as compared to the non-steamed catalyst ofExample 22.

EXAMPLE 24

A fluid catalytic cracking combustion promoter catalyst having Group AGeldart fluidization characteristics and substantially consisting ofparticles of less than 100 microns in mass average diameter was added toa commercial fluid bed incinerator facility at the Amoco Oil WhitingRefinery in Whiting, Ind. The combustion promoter catalyst was CCA-8 COpromoter manufactured by Amber Chemicals.

The FCC promoter catalyst was added directly to the FBI reactor bed inan amount to achieve a platinum concentration of 0.3 ppm by weight inthe bed. The carbon monoxide level in the FBI flue gas prior tointroduction of FCC promoter catalyst was 40 ppm weight at an FBIreactor vessel bed temperature of 1280° F. No noticeable reduction influe gas carbon monoxide level was observed.

The carbon monoxide level in the FBI flue gas was increased to 190 ppmby weight by the addition of fuel oil to the FBI feed. The FBI bedtemperature remained at 1280° F. Additional FCC promoter catalyst wasadded to the reactor vessel bed of the FBI to achieve a platinumconcentration in the bed of 1 ppm by weight. No noticeable reduction influe gas carbon monoxide level was observed.

This test illustrates that FCC promoter catalyst and catalysts withsimilar physical properties to FCC promoter catalysts are not suitablefor use in fluid bed incineration.

That which is claimed is:
 1. A combustion promoter catalyst comprising:apromoter support component comprising at least one member selected fromthe group consisting of mullite, spinel, alpha alumina, gamma alumina,delta alumina, eta alumina, silica, alumina, silica alumina, titania,zirconia, and sand; a promoter metal carried by said promoter supportcomponent wherein said promoter metal comprises at least one memberselected from the group consisting of the Group VIII metals and presentin an amount of from about 10 ppm by weight to about 5000 ppm by weightof said combustion promoter catalyst; said combustion promoter catalystconsisting essentially of particulate having a particle size of greaterthan 150 microns and having a Group B Geldart characterization.
 2. Thecombustion promoter catalyst of claim 1 wherein said promoter supportcomponent comprises a substrate and a substrate coating, said substratecomprising at least one member selected from the group consisting ofmullite, spinel, alpha alumina, and sand, and said substrate coatingcomprising at least one member selected from the group consisting ofsilica, alumina, titania, silica alumina, zirconia, gamma alumina, deltaalumina, and eta alumina.
 3. The combustion promoter catalyst of claim 1wherein said promoter support comprises at least one member selectedfrom the group consisting of alpha alumina, gamma alumina, silicaalumina, and silica.
 4. The combustion promoter catalyst of claim 1wherein said promoter metal comprises from about 50 ppm by weight toabout 3000 ppm by weight of said combustion promoter catalyst.
 5. Acombustion promoter catalyst comprising:a promoter support componentcomprising at least one member selected from the group consisting ofalpha alumina, gamma alumina, silica alumina, and silica; a promotermetal carried by said support component wherein said promoter metalcomprises at least one member selected from the group consisting of theplatinum metals and present in an amount from about 50 ppm by weight toabout 3000 ppm by weight of said combustion promoter catalyst; saidcombustion promoter catalyst consisting essentially of particulatehaving a particle size of greater than 150 microns and having a Group BGeldart characterization.
 6. The combustion promoter catalyst of claim 5wherein said promoter support comprises a substrate and a substratecoating wherein said substrate is alpha alumina and said substratecoating is gamma alumina.
 7. The combustion promoter catalyst of claim 5wherein said promoter support is gamma alumina.
 8. The combustionpromoter catalyst of claim 5 wherein said promoter metal comprises fromabout 100 ppm by weight to about 2500 ppm by weight of said combustionpromoter catalyst.
 9. The combustoin promoter catalyst of claim 5wherein said combustion promoter catalyst consists essentially ofparticulate having a particle size of greater than 200 microns.